1. Field of the Invention
The present invention relates to a method for producing a compound semiconductor substrate. In particular, it relates to a method for producing a compound semiconductor substrate, involving cutting a compound semiconductor substrate.
2. Description of the Related Art
As a method for producing a single crystal substrate from a compound semiconductor single crystal ingot such as a gallium nitride (GaN), aluminum nitride (AlN), silicon carbide (SiC), and the like, there is known a substrate production method, that includes preparing a not less than 150 mmφ diameter and not less than 300 mm long ingot, and cutting the ingot by pressing against a moving wire, wherein in the cutting step, the wire feeding speed is made faster in only a central portion in a diametrical direction of the ingot than at the beginning of cutting and near the end of cutting.
Since the above substrate production method makes the wire feeding speed faster in the central portion of the ingot, the wire wear is lessened, and the wire wobble can be reduced, and the bend of the cut surface of the resulting substrate can be made small.
Refer to JP-A-2008-188721, for example.
However, in the above substrate production method, when from an economical viewpoint, increasing the cutting speed of slicing a very hard compound semiconductor such as GaN, the roughness of the cut surface of the resulting substrate may be increased, or the damage to the crystal surface due to cutting may be significant.